- Metal-organic frameworks can capture, store and release chemical compounds like salts and ions in seawater.
- It has a wide internal surface area and sponge like crystals for trapping chemical compounds dissolved in water.
Do you know more than 783 million people in the world don’t have access to clean and safe drinking water? Around 443 million days are lost each year because of water-related diseases.
In an attempt to improve these disgusting stats, researchers at Monash University, Australia, have come up with a solution. They have developed a next-generation material, metal-organic frameworks (MOFs) that can capture, store and release chemical compounds like salt and ions in seawater.
These frameworks have an expansive internal surface area and sponge like crystals that can trap chemical compounds dissolved in water. This research has a potential to solve a major problem the world is facing today. So let’s dive deeper and try to find out what they’ve actually built.
The metal-organic framework membrane mimic the “ion selectivity” function (or filtering function) of organic cell membranes. It can perform a dual operation – removing salts from seawater and separating metal ions in an efficient and cost effective way. The study holds a potential for revolutionizing water filtering technique and mining industries.
Over half of the world’s water desalination is done through reverse osmosis membranes. The process we use today can be improved in terms of energy consumption – it could be decreased by a factor of 3. Since they don’t use selective ion transport in biological channels or ion dehydration, it has significant limitations.
At present, mining industries are working to develop membrane processes to decrease water pollution and recover useful metals. Lithium-ion batteries are the major source for powering handheld devices, however, the rising demand at the current consumption rates would likely to require lithium production from other sources as well, like recovery from waste process streams and salt water.
The extraction/purification through lithium from such complex liquid systems would’ve great economic impacts. Fortunately, this is now feasible. Using this study one can address the challenges and issues related to water desalination. The study opens a door for environmentally sustainable and more energy efficient way.
Reference: Science Advances | doi:10.1126/sciadv.aaq0066
More specifically, the researchers have demonstrated MOF membranes, including UiO-66 and ZIF-8 membranes with uniform subnanometer pores comprising of nanometer-sized cavities and angstrom-sized windows for super-fast selective transport of alkali metal ions.
The tiny windows act as ion selectivity filters to select alkali metal ions, and the cavities function as ion conductive pores to fast ion transportation. Both UiO-66 and ZIF-8 membranes show a RbCl/LiCL selectivity of nearly 1.8 and 4.6 respectively, which is by the way far higher than RbCl/LiCL selectivity of 0.8 and 0.6 obtained in conventional porous membranes.
Moreover, according to molecular dynamics simulations, fast and selective ion transportation in ZIF-8 is based on partial dehydration effects.
This is just a beginning of the potential for this approach. The researchers will continue to investigate how lithium ion selectivity of these membranes could be applied in the future.
Moreover, produced water from shale gas fields is rich in lithium, in Texas. Advanced approaches like this could really convert this waste stream into a resource recovery opportunity.